Create new script to start frontend returning mocked data

[paulovmr]

The current npm run start:dev should run the frontend querying the backend directly.
A new npm run start:dev:mock should be created to use hard-coded mocks in the frontend.

This task includes calling the appropriate backend services for all currently mocked actions.

[paulovmr]

/assign
/area frontend
/area v2

[paulovmr]

/assign @caponetto

[google-oss-prow]

@paulovmr: GitHub didn't allow me to assign the following users: caponetto.

Note that only kubeflow members with read permissions, repo collaborators and people who have commented on this issue/PR can be assigned. Additionally, issues/PRs can only have 10 assignees at the same time.
For more information please see the contributor guide

In response to this:

/assign @caponetto

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[caponetto]

/assign